Comparative Patterns of Physiological Responses to Cold Resistance of Zanthoxylum bungeanum Maxim

The pepper plant Zanthoxylum bungeanum Maxim (Z. bungeanum) is an economically important cash crop with both nutritional and medicinal value, but low-temperatures are a major factor affecting its normal growth and quality. Measuring its physiological and biochemical parameters is essential to distinguish clues that can help agriculturists select the proper types of Z. bungeanum with considerable tolerance to low-temperature stress. This study aims to investigate the cold tolerance of different Z. bungeanum types and provide the best cultivation area. Six excellent cultivars were compared in a low-temperature environment and the membership function method was used to analyze the relevant indicators. The results revealed a significant negative correlation between the superoxide dismutase (SOD) activity and malondialdehyde (MDA) content (p < 0.01), with both the SOD and peroxidase (POD) activity increasing during the early stages of exposure to low-temperature stress. The MDA and proline (Pro) contents increased with longer durations of low-temperature stress, whereas the chlorophyll (Chl) content decreased. Logistic modeling showed that the low-temperature semi-lethal temperature LT50 of leaf conductivity was from −12.7°C to 1.2°C. By means of a membership function analysis, the cold-tolerance abilities of the six cultivars of Z. bungeanum were comprehensively evaluated and were ranked as follows: ‘Xinongwuci’ and ‘Wucijiao’ are cold hardy, ‘Shaocidahongpao’ and ‘Huanggai’ are medium cold hardy, and ‘Shizitou’ and ‘Gelaowuci’ are low-temperature-sensitive cultivars. This study provides the necessary empirical basis for the selection and promotion of cold-resistant cultivars of Z. bungeanum.